/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * fs/semaphore/sem_open.c
 *
 *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <stdint.h>
#include <stdarg.h>
#include <stdio.h>
#include <fcntl.h>
#include <semaphore.h>
#include <string.h>
#include <sched.h>
#include <errno.h>

#include <tinyara/kmalloc.h>
#include <tinyara/semaphore.h>
#include <tinyara/fs/fs.h>

#include "inode/inode.h"
#include "semaphore/semaphore.h"

#ifdef CONFIG_FS_NAMED_SEMAPHORES

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: sem_open
 *
 * Description:
 *   This function establishes a connection between named semaphores and a
 *   task.  Following a call to sem_open() with the semaphore name, the task
 *   may reference the semaphore associated with name using the address
 *   returned by this call.  The semaphore may be used in subsequent calls
 *   to sem_wait(), sem_trywait(), and sem_post().  The semaphore remains
 *   usable until the semaphore is closed by a successful call to sem_close().
 *
 *   If a task makes multiple calls to sem_open() with the same name, then
 *   the same semaphore address is returned (provided there have been no
 *   calls to sem_unlink()).
 *
 * Parameters:
 *   name  - Semaphore name
 *   oflags - Semaphore creation options.  This may either or both of the
 *     following bit settings.
 *     oflags = 0:  Connect to the semaphore only if it already exists.
 *     oflags = O_CREAT:  Connect to the semaphore if it exists, otherwise
 *        create the semaphore.
 *     oflags = O_CREAT|O_EXCL:  Create a new semaphore
 *        unless one of this name already exists.
 *   Optional parameters.  When the O_CREAT flag is specified, two optional
 *     parameters are expected:
 *     1. mode_t mode (ignored), and
 *     2. unsigned int value.  This initial value of the semaphore. Valid
 *        initial values of the semaphore must be less than or equal to
 *        SEM_VALUE_MAX.
 *
 * Return Value:
 *   A pointer to sem_t or -1 (ERROR) if unsuccessful.
 *
 * Assumptions:
 *
 ****************************************************************************/

FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
{
	FAR struct inode *inode;
	FAR const char *relpath = NULL;
	mode_t mode;
	FAR struct nsem_inode_s *nsem;
	FAR sem_t *sem = (FAR sem_t *)ERROR;
	char fullpath[MAX_SEMPATH];
	unsigned value;
	int errcode;
	int ret;

	/* Make sure that a non-NULL name is supplied */

	if (name) {
		/* The POSIX specification requires that the "check for the existence
		 * of a semaphore and the creation of the semaphore if it does not
		 * exist shall be atomic with respect to other processes executing
		 * sem_open()..."  A simple sched_lock() should be sufficient to meet
		 * this requirement.
		 */

		sched_lock();

		/* Get the full path to the semaphore */

		snprintf(fullpath, MAX_SEMPATH, CONFIG_FS_NAMED_SEMPATH "/%s", name);

		/* Get the inode for this semaphore.  This should succeed if the semaphore
		 * has already been created.
		 */

		inode = inode_find(fullpath, &relpath);
		if (inode) {
			/* It exists.  Verify that the inode is a semaphore */

			if (!INODE_IS_NAMEDSEM(inode)) {
				errcode = ENXIO;
				goto errout_with_inode;
			}

			/* It exists and is a semaphore.  Check if the caller wanted to
			 * create a new semaphore with this name.
			 */

			if ((oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) {
				errcode = EEXIST;
				goto errout_with_inode;
			}

			/* Return a reference to the semaphore, retaining the reference
			 * count on the inode.
			 */

			sem = &inode->u.i_nsem->ns_sem;

		} else {
			va_list ap;

			/* The semaphore does not exists.  Were we asked to create it? */

			if ((oflags & O_CREAT) == 0) {
				/* The semaphore does not exist and O_CREAT is not set */

				errcode = ENOENT;
				goto errout_with_lock;
			}

			/* Create the semaphore.  First we have to extract the additional
			 * parameters from the variable argument list.
			 * REVISIT:  Mode parameter is not currently used.
			 */

			va_start(ap, oflags);
			mode = va_arg(ap, mode_t);
			value = va_arg(ap, unsigned);
			va_end(ap);

			UNUSED(mode);

			/* Check the semaphore value */

			if (value > SEM_VALUE_MAX) {
				errcode = EINVAL;
				goto errout_with_lock;
			}

			/* Create an inode in the pseudo-filesystem at this path */

			inode_semtake();
			ret = inode_reserve(fullpath, &inode);
			inode_semgive();

			if (ret < 0) {
				errcode = -ret;
				goto errout_with_lock;
			}

			/* Allocate the semaphore structure (using the appropriate allocator
			 * for the group)
			 */

			nsem = group_malloc(NULL, sizeof(struct nsem_inode_s));
			if (!nsem) {
				errcode = ENOMEM;
				goto errout_with_inode;
			}

			/* Link to the inode */

			inode->u.i_nsem = nsem;
			nsem->ns_inode = inode;

			/* Initialize the inode */

			INODE_SET_NAMEDSEM(inode);
			inode->i_crefs = 1;

			/* Initialize the semaphore */

			sem_init(&nsem->ns_sem, 0, value);

			/* Return a reference to the semaphore */

			sem = &nsem->ns_sem;
		}

		sched_unlock();
	}

	return sem;

errout_with_inode:
	inode_release(inode);
errout_with_lock:
	set_errno(errcode);
	sched_unlock();
	return (FAR sem_t *)ERROR;
}

#endif							/* CONFIG_FS_NAMED_SEMAPHORES */
